x86: cleanup x86_cpu_to_apicid references

Clean up references to x86_cpu_to_apicid.  Removes extraneous
comments and standardizes on "x86_*_early_ptr" for the early
kernel init references.

Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>